In all, 83 of 177 patients with low-tone SD unaccompanied by vertigo had recurrent hearing loss; 15 of the 83 developed vertiginous attacks. The remaining 94 patients had a single episode. Three of the seven patients with low-tone SD accompanied by vertigo had recurrent hearing loss; two of the three were subsequently confirmed to have Meniere's disease. The other four had a single episode. No difference in rate of progress from SD to Meniere's disease was observed among the low-tone and the high-tone SD groups. The average -SP/AP of each group with a single episode is smaller than that of other groups with recurrent episodes and Meniere's disease.

Our results indicate that idiopathic sudden low-tone sensorineural hearing loss without vertigo has a high recurrence rate when vestibular alteration and endolymphatic hydrops are detected on initial examination. A combination of nystagmus detection and ECochG test well characterizes the pathophysiology of sudden low-tone sensorineural hearing loss without vertigo.

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The combination of ECochG and the glycerol and furosemide tests was helpful in diagnosing endolymphatic hydrops (ELH). ECochG and the glycerol test were effective tools for predicting the progression to definite MD in patients with atypical MD, sudden hearing loss and other cochleovestibular diseases. Our test results also indicated that the pathological state of atypical MD included both non-ELH and ELH.

The recovery rate at the initial treatment was 47.6% for non-ALHL and 62.9% for ALHL. A Kaplan-Meier plot indicated that cumulative recurrence rates for non-ALHL were 20.2% at 1 year and 43.5% at 5 years, whereas the rates for ALHL were 12.2% at 1 year and 31.3% at 5 years. There was no statistically significant difference between the two patient groups.